I think I started working with swybrid picking in about 2016, after watching the Marshall Harrison interview here on CTC and some of Marshall’s YouTube videos.
I was already adept at RDT-based mixed escape and DBX alternate picking, USX and hybrid picking. I was never very comfortable with full-on sweeping and economy picking, and my hybrid picking wasn’t totally integrated with my other picking forms. Marshall’s CTC interview and his YouTube videos opened up a whole new world of possibilities for me.
This I can answer.
Marshall is capable of mixed escape “directional” picking, where every string change is either a sweep or an inside change. Marshall calls this “Jimmy Bruno Economy Picking.” If we take a basic A major scale shape like you’re suggesting, we have the picking solutions:
|-----------------------------5-7-9-
|-----------------------5-7-9-------
|-----------------4-6-7-------------
|-----------4-6-7-------------------
|-----4-5-7-------------------------
|-5-7-------------------------------
d u d u d d u d d u d d u d d u d
or
u d d u d d u d d u d d u d d u d
The first option is one way economy (USX) which the second option is strictly sweepable (that is, it follows the Gambale economy rules).
Marshall is totally capable of either, but he very clearly has a preference for the second option. I would strongly suspect that if Marshall found himself needing to play this scale, he would have arranged whatever he played before it so that the scale can begin with an upstroke.
If the scale could not begin on the upstroke and the scale had to be played starting on a downstroke, I suspect that Marshall would prefer to change the fretting to incorporate a position shift to achieve a sequence which follows the Gambale rules. So, the sequence
2 4 1 2 4 1 3 4 1 3 4 1 2 4 1 2 4
|-----------------------------5-7-9-
|-----------------------5-7-9-------
|-----------------4-6-7-------------
|-----------4-6-7-------------------
|-----4-5-7-------------------------
|-5-7-------------------------------
d u d u d d u d d u d d u d d u d
would become
2 4s4 1 2 4 1 2 4 1 2 4 1 3 4 1 3
|--------------------------------7-9-
|-------------------------7-9-10-----
|-------------------6-7-9------------
|-------------6-7-9------------------
|-------5-7-9------------------------
|-5-7-9------------------------------
d u d d u d d u d d u d d u d d u
or some other variation on this idea. Marshall’s fretting hand is more than capable of the task.
So, if Marshall is able to play this sequence without hybrid picking, does that mean he wouldn’t hybrid pick at all? Maybe not. Marshall could choose to incorporate a single hybrid picked note to change the position of the inside change, as follows:
|-----------------------------5-7-9-
|-----------------------5-7-9-------
|-----------------4-6-7-------------
|-----------4-6-7-------------------
|-----4-5-7-------------------------
|-5-7-------------------------------
d u m d u d u d d u d d u d d u d
Why would he do this? Marshall’s picking movement is quite flat. It appears to me that he has a bias towards DSX. For ascending economy he needs to supinate very slightly to achieve a downward slant. If he were to begin this sequence falt or with a slight DSX, the pluck with the middle finger can involve a subtle roll, bringing him into a more supination and facilitating USX one way economy for the rest of the sequence.
Marshall certainly could play the sequence repeating mdu on each string
|-----------------------------5-7-9-
|-----------------------5-7-9-------
|-----------------4-6-7-------------
|-----------4-6-7-------------------
|-----4-5-7-------------------------
|-5-7-------------------------------
d u m d u m d u m d u m d u m d u
however, I would doubt that he would do this unless he had a very specific reason. I could see this pattern facilitating a more comfortable turnaround , for example.
The alternative you’ve given
|-----------------------------5-7-9-
|-----------------------5-7-9-------
|-----------------4-6-7-------------
|-----------4-6-7-------------------
|-----4-5-7-------------------------
|-5-7-------------------------------
d u m u d d u d d u d d u d d u d
is basically a non-starter. An upstroke can follow a hybrid pluck, but not on the same string. After the plucked note (C#) with the middle finger, the tip of the pick will be above the A string. It’s direction of travel towards the next note (D) is downward. Attempting to play an upstroke here is essentially equivalent to doing two sequential upstrokes on the same string.
Here’s an example of a pattern using u after m. It’s DSX+hybrid, the trick here is not to let the pick escape the strings when the middle finger plucks.
|-------------|-------------|
|-------------|-------------|
|-----6-------|-------------|
|-7-9---------|-----6-------|
|-------7-9-5-|-7-9---------|
|-------------|-------7-9-5-|
d u m u d u d u m u d u
Done correctly, the umu here feels similar to an upstroke sweep. People familiar with my work will know that this is an EDC sequence.
It’s important to understand that we don’t always need to use full two-way swybrid. If we can incorporate the hybrid picked notes after the upstroke in either DSX or USX, we can solve a lot of the “bad cases” in each system.
In DSX it’s totally straightforward. The only “bad case” is when we want to play a note on a higher string after an upstroke, we can do whatever we want after a downstroke (because we’re escaped) and if we want to play a note on a lower string after an upstroke we can use an upstroke sweep. Hybrid picking solves this bad case immediately, the higher string is naturally plucked by the middle finger.
In USX it’s a little more subtle, but plucking with the middle finger after an upstroke can be used to solve the case that Chris Brooks calls “the lone note exception.” I think seamless USX+hybrid demands a dart-thrower movement, the fingers won’t be in a position to hybrid pick with other USX forms.
It’s also worth noting that hybrid picking offers some really unusual capabilities. The hybrid picked note after the upstroke does not need to be on an adjacent string, so we can easily skip strings. Also, if we pluck with the middle and ring fingers simultaneously, we can incorporate double-stops.
My brain still can’t understand how to pluck fastly after an upstroke 
Those techniques that you mentioned are kinda easy when you only use one of them, but swybryd is like multitasking i guess, maybe that’s why it’s frustrating for me 
